• Proceedings of the Safety Management and Science Conference
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• 2011.04a
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• pp.67-77
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• 2011

The railroad system must ensure not only the safety of facilities but also the prevention of natural and environmental disasters. The infrastructure must be strengthened in order to prevent rail damage by natural disasters and other causes. Thus, it would be able to prevent damage due to such natural factors like heavy rain and snow fall, wind, and catastrophic earthquakes. It seems that it would be the best way to install safety facilities throughout the entire length of a route, but one would not be able to provide for the costs involved in this approach. Therefore, these facilities must be installed at selected locations that is the most vulnerable to disasters. In this paper we propose the examples of both foreign and domestic methods in order to prevent from damages caused by the above-mentioned natural disasters and others.

• Journal of Korean Society of Rural Planning
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• v.4 no.1
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• pp.63-74
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• 1998

The objective of this study is the investigation and analysis of information on the conservation and the sustainable use of coastal wetlands based on the awareness of local residents in Kang-hwa island, Tae-an and Seo-chon. The results are summarized as follows: The degree of the satisfaction on the natural environment is in the order of Tae-an, Kang-hwa and Seo-chon. This order is accorded with the order of the goodness of natural environment. The order for the degree of the satisfaction on the living environment is same as the order for the satisfaction degree on the natural environment. Especially, residents of Seo-chon are not satisfied with the living environment. The residents of all regions are not satisfied with the socio $.$ economic environment. The local resident of Kang-hwa and Tae-an, where natural environment is well-conserved, prefer conservation to development of the region. On the other hand, the local residents of Seo-chon have relatively low preference for conservation of the region. These results show the following consideration for the ideal method of management for the conservation and sustainable development of coastal wetlands. In case of Kang-hwa island, where the, condition the natural environment is well conserved, should be managed with the minimum development with maintenance of the current state must be driven.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04b
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• pp.289-291
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• 2002

Host of source separation methods focus on stationary sources so higher-order statistics is necessary In this paler we consider a problem of source separation when sources are second-order nonstationary stochastic processes . We employ the natural gradient method and develop learning algorithms for both 1inear feedback and feedforward neural networks. Thus our algorithms possess equivariant property Local stabi1iffy analysis shows that separating solutions are always locally stable stationary points of the proposed algorithms, regardless of probability distributions of

• Korean Institute of Interior Design Journal
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• v.20 no.5
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• pp.245-253
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• 2011

As interests towards health rapidly increase recently, interests and demand for hospital interior space are increasing as well. Therefore, most of today's hospitals that have been functionally designed are transforming into healing environments that consider psychological aspects, in order to assist patients forget about fear, desperation and have peace of mind. With such creation method of healing environment, natural elements can be applied to spaces in order to allow patients feel vitality, hope and adapt positive thinking, and these can eventually lead to affluent fusion of humans, nature and space. Through case analyses of how natural elements are applied to hospital's interior space, this study understands its characteristics. According to the findings, nature is largely classified into light, water, plant, stone/soil, and its application methods can be classified into center, transition, continuity, division, opening and closure. As evident from case analyses, application of natural elements to hospital's interior space promotes exchanges among patients through community formation, and achieves the effect of spatial concentration and public place. Also, ambiguity of exterior and interior boundary creates a sense of expansion and continuous effect, and can also provide a healing environment that can fully absorb natural environment open to patients. This study aims to be of service when designing hospital's interior space, with its natural element application method for healing environment research, and wishes for continuous studies on healing environments with more diverse methods.

• Structural Monitoring and Maintenance
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• v.6 no.2
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• pp.85-101
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• 2019

The effects of foundation scour depth and riverbed condition on the natural frequencies of a typical cross-river integral abutment bridge have been studied. The conventional operational modal analysis technique has been employed in order to extract the modal properties of the bridge and the results have been used in the Finite Element (FE) model updating procedure. Two tests have been carried out in two different levels of water and wet condition of the riverbed. In the first test, the riverbed was in dry condition for two subsequent years and the level of water was 10 meter lower than the natural riverbed. In the second test, the river was opened to water flow from the upstream dam and the level of water was 2 meter higher than the natural riverbed. The results of these two tests have also been used in order to find to what extend the presence of water flow in the river and saturation of the surrounding soil affect the bridge natural frequencies. Finally, the updated FE model of the bridge has been applied in a series of parametric analyses incorporating the effect of piles' relative scour depth on the bridge natural frequency of the first four vibration modes.

• Steel and Composite Structures
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• v.49 no.1
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• pp.81-89
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• 2023

A simplified calculation method of natural vibration characteristics of high-speed railway multi-span bridge-longitudinal ballastless track system is proposed. The rail, track slab, base slab, main beam, bearing, pier, cap and pile foundation are taken into account, and the multi-span longitudinal ballastless track-beam-bearing-pier-cap-pile foundation integrated model (MBTIM) is established. The energy equation of each component of the MBTIM based on Timoshenko beam theory is constructed. Using the improved Fourier series, and the Rayleigh-Ritz method and Hamilton principle are combined to obtain the extremum of the total energy function. The simplified calculation formula of the natural vibration frequency of the MBTIM under the influence of vertical and longitudinal vibration is derived and verified by numerical methods. The influence law of the natural vibration frequency of the MBTIM is analyzed considering and not considering the participation of each component of the MBTIM, the damage of the track interlayer component and the stiffness change of each layer component. The results show that the error between the calculation results of the formula and the numerical method in this paper is less than 3%, which verifies the correctness of the method in this paper. The high-order frequency of the MBTIM is significantly affected considering the track, bridge pier, pile soil and pile cap, while considering the influence of pile cap on the low-order and high-order frequency of the MBTIM is large. The influence of component damage such as void beneath slab, mortar debonding and fastener failure on each order frequency of the MBTIM is basically the same, and the influence of component damage less than 10m on the first fourteen order frequency of the MBTIM is small. The bending stiffness of track slab and rail has no obvious influence on the natural frequency of the MBTIM, and the bending stiffness of main beam has influence on the natural frequency of the MBTIM. The bending stiffness of pier and base slab only has obvious influence on the high-order frequency of the MBTIM. The natural vibration characteristics of the MBTIM play an important guiding role in the safety analysis of high-speed train running, the damage detection of track-bridge structure and the seismic design of railway bridge.

• Ocean Systems Engineering
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• v.7 no.1
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• pp.53-74
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• 2017

Ship shaped FPSO (Floating Production, Storage and Offloading) units are the most commonly used floating production units to extract hydrocarbons from reservoirs under the seabed. These structures are usually much larger than general cargo ships and have their natural frequency outside the wave frequency range. This results in the response to first order wave forces acting on the hull to be negligible. However, second order difference frequency forces start to significantly impact the motions of the structure. When the difference frequency between wave components matches the roll natural frequency, the structure experiences a significant roll motion which is also termed as second order roll. This paper describes the theory and numerical implementation behind the calculation of second order forces and motions of any general floating structure subjected to waves. The numerical implementation is validated in zero speed case against the commercial code OrcaFlex. The paper also describes in detail the popular approximations used to simplify the computation of second order forces and provides a discussion on the limitations of each approximation.

• The Journal of Engineering Geology
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• v.31 no.3
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• pp.367-380
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• 2021

This study evaluated the stability through a three-dimensional numerical analysis method when a natural cave exists under a road in operation in Jeju Island. In order to confirm the geometric and geotechnical characteristics of the Jeju natural cave passing under the road, existing geotechnical survey reports were collected, and were studied the characteristics. In order to evaluate the effect of vehicle vibration loading on the natural cave in Jeju, three-dimensional numerical analysis was performed considering discontinuities. Through this, the stability of roads and caves with respect to vehicle speed and the depth of cover (distance from the road to the top of the natural cave) was evaluated and countermeasures were suggested. In order to secure the long-term stability of the Jeju natural cave that penetrates the lower part of the road, it was evaluated that systematic management such as long-term measurement management, reinforcement measures, and emergency measures would be necessary depending on the depth of the cover.

• Steel and Composite Structures
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• v.35 no.1
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• pp.43-59
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• 2020

In this study, free vibration analysis of laminated composite parabolic thick plate frames by using finite element method is introduced. Governing equations of an eigenvalue problem are obtained from First Order Shear Deformation Theory (FSDT). Finite element method is employed to obtain natural frequency values from the governing differential equations. The frames consist of two flat square plates and one singly curved plate. Parameters like radii of curvature, aspect ratio, ply orientation and boundary conditions are investigated to understand their effect on dynamic behavior of such a structure. In addition, multi-bay structures of such geometry with different stacking order are also taken into account. The composite frame structures are also modeled and simulated via ANSYS to verify the accuracy of the present study.

• Korean Membrane Journal
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• v.2 no.1
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• pp.48-55
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• 2000

In order to improve organic vapor separation efficiency of polydimethylsiloxane (PDMS) membrane, various zeolites (zeolite 4A, zeolite 13X and natural zeolite) were introduced into a thin PDMS film. The measurements of permeability and selectivity of zeolite-filled PDMS membranes were carried out with a CO$_2$gas and a CO$_2$gas/acetic acid vapor mixture, respectively. The CO$_2$permeability of zeolite-filled membranes decreased with increasing zeolite content and then recovered up to 30 wt% content. The effect of zeolite type on the improvement of CO$_2$permeability was found to be in the order of zeolite 13X > natural zeolite > 4A. The CO$_2$selectivity of zeolite-filled membranes was enhanced up to 9 times compared with the selectivity of a pure (unfilled) PDMS membrane. The effect of zeolite type on the improvement of CO$_2$selectivity was found to be in the order of natural zeolite > zeolite 13X > zeolite 4A.